Methods and compositions for coating aluminum substrates
The present invention relates to methods and compositions for coating aluminum substrates. In an embodiment, the invention includes a method of applying a coating on an aluminum substrate including contacting the aluminum substrate with a first solution. The first solution can include a zinc metal salt, a sugar acid or alkali metal salt thereof, and an alkali metal hydroxide. The method can also include contacting the aluminum substrate with a second solution. The second solution can include a molybdate salt, an alkanolamine, and a fluorine acid. Other embodiments are also included herein.
1. A kit for applying a coating exhibiting black color stability for a period of 60 days to an aluminum substrate, the kit comprising:
a first solution comprising
at least about 2 grams per liter of a zinc metal salt;
at least about 2 grams per liter of a sugar acid selected from the group consisting of gluconic acid, glucoheptonic acid, and alkali metal salts thereof;
at least about 20 grams per liter of an alkali metal hydroxide; and
a second solution comprising
at least about 20 grams per liter of a molybdate salt;
at least about 10 grams per liter of an alkanolamine; and
at least about 2 grams per liter of a fluorine acid.
2. The kit of claim 1 , the first solution further comprising
at least about 0.5 grams per liter of an iron metal salt;
at least about 2 grams per liter of a carboxylic acid or alkali metal salt thereof; and
at least 1 gram per liter of an oxidizing agent.
3. A composition for applying a coating exhibiting black color stability for a period of 60 days on an aluminum substrate the solution comprising:
at least about 2 grams per liter of a zinc metal salt;
at least about 0.5 grams per liter of an iron metal salt;
at least about 2 grams per liter of a carboxylic acid or alkali metal salt thereof;
at least about 2 grams per liter of a sugar acid selected from the group consisting of gluconic acid, glucoheptonic acid, and alkali metal salts thereof;
at least about 20 grams per liter of an alkali metal hydroxide; and
at least about 1 gram per liter of an oxidizing agent.
4. The kit of claim 1 , the first solution further comprising:
an iron metal salt,
a carboxylic acid or alkali metal salt thereof, and
an oxidizing agent.
5. The kit of claim 1 , the zinc metal salt comprising zinc (II) oxide.
6. The kit of claim 4 , the iron metal salt comprising an iron (III) salt.
7. The kit of claim 6 , the iron (III) salt comprising FeCl 3 .
8. The kit of claim 2 , the carboxylic acid selected from the group consisting of glycolic acid, malic acid, tartaric acid, and citric acid.
9. The kit of claim 2 , the carboxylic acid or alkali metal salt thereof comprising one or more of sodium tartrate, potassium tartrate, and sodium-potassium tartrate.
10. The kit of claim 1 , the alkali metal hydroxide selected from the group consisting of sodium hydroxide, potassium hydroxide, and lithium hydroxide.
11. The kit of claim 2 , the oxidizing agent comprising an alkali metal nitrate.
12. The kit of claim 1 , the molybdate salt comprising ammonium heptamolybdate.
13. The kit of claim 1 , the alkanolamine selected from the group consisting of monoethanolamine, triethanolamine, and 2-amino-2-methyl-1-propanol.
14. The kit of claim 1 , the alkanolamine comprising 2-amino-2-methyl-1-propanol.
15. The kit of claim 1 , the fluorine acid selected from the group consisting of fluoroboric acid and fluorosilicic acid.